1. Field of the Invention
The present invention relates to a method and apparatus for lining a pipe by applying a liner bag on the inner wall of the pipe, and in particular to a method and apparatus for lining a branch pipe branching off a main pipe.
2. Description of the Related Art
When an underground pipe, such as pipelines and passageways, becomes defective or too old to perform properly, the pipe is repaired and rehabilitated without digging the earth to expose the pipe and disassembling the sections of the pipe. This non-digging method of repairing an underground pipe has been known and practiced commonly in the field of civil engineering. Typically, the method is disclosed by Japanese Provisional Patent Publication (Kokai) No. 60-242038.
According to the method described in the above-mentioned publication, the pipe repair method comprises inserting a sufficiently long tubular flexible liner bag into the pipe to be repaired by means of a pressurized fluid, like air and water. The tubular liner bag is made of a flexible resin-absorbent material impregnated with a thermosetting resin, and has the outer surface covered with an impermeable plastic film.
More particularly, according to the publication, the tubular flexible liner bag is closed at one end and open at the other; the tubular flexible liner bag is first flattened, then, the closed end of the tubular liner bag is tied to a control rope; the open end of the tubular liner bag is made to gape wide and hooked (anchored) at the end of the defective or old pipe in a manner such that the wide-opened end of the liner completely and fixedly covers and closes the pipe end; a portion of the liner is pushed into the pipe; then, the pressurized fluid is applied to the the portion of the tubular liner such that the fluid urges the tubular liner to enter the pipe. Since one end of the tubular liner is hooked at the end of the pipe, it remains there while the rest of the flexible liner bag is turned inside out as it proceeds deeper in the pipe. (Hereinafter, this manner of procedure shall be called "everting".) When the entire length of the tubular liner bag is everted (i.e., turned inside out) into the pipe, the control rope holds the closed end of the tubular liner bag to thereby control the length of the tubular liner in the pipe. Then, the everted tubular liner is pressed against the inner wall of the pipe by the the pressurized fluid, and the tubular flexible liner is hardened as the thermosetting resin impregnated in the liner is heated, which is effected by heating the fluid filling the tubular liner bag by means of a hot steam, etc. It is thus possible to line the inside wall of the defective or old pipe with a rigid liner without digging the ground and disassembling the pipe sections.
This method is applicable to a pipe branching out from a main pipe as well, and how it is conducted will be described next with reference to FIG. 7.
FIG. 7 is a cross-sectional view showing a conventional method for lining a branch pipe. A pressure bag 107 is inserted into a main pipe 120. Since this pressure bag 107 must be separated from a branch pipe liner bag 101, a sealed tube 111 must be connected to the pressure bag 107 for applying a pressure to the branch pipe liner bag 101.
Then, compressed air or the like is supplied into the pressure bag 107. The sealed tube 111 and the branch pipe liner bag 101 are everted in a branch pipe 121, and the branch pipe liner bag 101 is heated to harden a hardenable resin impregnated therein while the illustrated state is held unchanged. Thereafter, when the sealed tube 111 is pulled out from the branch pipe 121 (branch pipe liner bag 101), the branch pipe has been lined by the hardened branch pipe liner bag 101. Thus, the inner wall of the branch pipe 121 is repaired.
With the above-mentioned conventional method, however, sealed tubes of proper lengths must be prepared depending upon variations in length of branch pipes every time a repair operation is required, wherein a problem arises that the sealed tube must be exchanged such that a suitable length is provided for a branch pipe to be repaired. Additionally, if a steeply angled bent portion is included in a branch pipe, the sealed tube may be caught by the bent portion, thus preventing the same from being extracted from the branch pipe.
To overcome the above-mentioned problems, a method for lining a branch pipe as shown in FIGS. 8 and 9 has been proposed (in Japanese Patent Application No. 3-156096). This method will hereinafter be described with reference to these drawings.
As shown in FIG. 8, a work robot 206 is introduced into a main pipe 220, and a set nozzle 211 of the work robot 206 and a pressure bag 207 are connected by a guide tube 208. Inside the guide tube 208, there is arranged a peel-back tube 231 which enables an air-tight connection between the pressure bag 207 and the branch pipe liner bag 201. More specifically, one end of the peel-back pipe 231 is attached to the pressure bag 207, while the other end of the same is temporarily adhered to the inner wall of the branch pipe liner bag 201 such that the peel-back pipe 231 may be easily detached therefrom after the repair operation is completed.
After a flange 205 of the branch pipe liner bag 201 is positioned at a peripheral edge of an opening formed through the branch pipe 221, when a compressor, not shown, is driven to supply compressed air to the pressure bag 207 and an air mat 232, the air mat 232 is inflated as shown in FIG. 8 to cause the flange 205 of the branch pipe liner bag 201 to tightly contact with the peripheral edge of the opening in the branch pipe 221. The branch pipe liner bag 201 located inside the pressure bag 207, receiving the pressure of the compressed air supplied into the pressure bag 207, is gradually everted and inserted into the branch pipe 221 in the direction indicated by the white arrow in the drawing.
When the eversion and insertion of the branch pipe liner bag 201 into the branch pipe 221 have been completed, a cap 233 is attached to an open end of the branch pipe liner bag 201, as shown in FIG. 9, to which an air hose 234 is connected to supply compressed air into the branch pipe liner bag 201, whereby the branch pipe liner bag 201 is pressed against the inner wall of the branch pipe 221. In this state, when a pump 235 is driven to inject hot water stored in a tank 236 into the branch pipe liner bag 201 through a hot water hose 237, the hot water provides heat to a thermosetting resin impregnated in the branch pipe liner bag 201 to cause the same to be cured. In this manner, the inner wall of the branch pipe 221 is lined with the cured branch pipe liner bag 201, thus completing the repair operation of the branch pipe 221.
After the branch pipe 221 has been lined as described above, hot water within the branch pipe liner bag 201 is extracted, and the pressure bag 207 is moved in the direction indicated by the arrows in FIG. 10. Then, since the pressure bag 207 and the work robot 206 are coupled through the guide tube 208, the work robot 206 is also moved together with the pressure bag 207, whereby the peel-back tube 231 temporarily adhered to the branch pipe liner bag 201 is peeled off from the temporarily adhered portion and then moved inside the main pipe 220 together with the pressure bag 207 and so on.
According to the method for lining a branch pipe as described above, since the air-tight connection between the pressure bag 207 and the branch pipe liner bag 201 is achieved by the peel-back tube 231, this method is advantageous in that the same peel-back tube 231 may be used for branch pipes of any length; the conventionally employed sealed tube 111 (see FIG. 7) can be removed; and steeply sloped, long, or largely curved branch pipes may be efficiently lined in a similar manner.
However, with the foregoing method for lining a branch pipe, when the peel-back tube 231 is peeled off from the branch pipe liner bag 201 as shown in FIG. 10, the temporarily adhered portion of the peel-back tube 231 may not be peeled and remain in the branch pipe liner bag 201, and the remaining portion may hinder a fluid from flowing inside the branch pipe 221.